Ahmadinejad differs from Hitler on a number of major grounds.
To begin with, Ahmadinejad is known as a grassroots leader or fighter, not an agent or collaborator of big business, as would be the case with fascist or fascistic figures and characters. Indeed, he came to power by challenging and running against the presidential candidate of big business, whereas fascist leaders like Hitler or Mussolini were promoted by big business.
Second, Hitler represented an expansionist imperial power. By contrast, Ahmadinejad (and the Iranian government in general) represent an anti-imperialist challenge or force in the Middle East that harbors no expansionist ambitions or territorial claims.
Third, Hitler was an unrivaled and unchallenged dictator. He had complete monopoly of power; not only commanding the German armed forces, but also controlling all the branches of government and, indeed, the entire German society. By contrast, Ahmadinejad is not a dictator; he is an elected president without much power. The real power rests with the "Supreme Leader," Ayatollah Ali Khamenei, who is commander in chief of all of Iran's armed forces. Khamenei has the final say on all major foreign policy issues.
Ahmadinejad is also constantly and relentlessly challenged by both the parliament and the Judiciary. For example, the legislature rejected more than two-thirds of his recommendations for ministers, which meant that it took nearly a year before his cabinet was fully staffed.
"Distorting Fascism to Demonize Iran"
By Ismael Hossein-zadeh